Rotate the four cogs 90° in the Z axis to stand them up. Delete History and Reset Transformation (Fig.14).
You now have your four basic prototype cogs, ready to create the gear system. All the other cogs in the system will be duplicates of these four prototypes.
Creating your First Gear Combination
The next objective is to create a gear combination. This requires two different sized cogs connected to a spindle (cylinder), as indicated in Fig.15.
The example in Fig.13 combines cog10 (10 teeth) with cog30 (30 teeth).
Duplicate cog10 and cog30 - Ctrl + [d]. Then align them using the Move tool [w] with
Point Snap [v] pressed (Fig.16).
Before we proceed with the tutorial, this is a convenient time to consider the size of the cogs and relationship between them. Look at Fig.16. The radius of cog30 (large) is three times bigger than cog10 (small). Likewise, the number of teeth on cog30 is three times as many as cog10.
The most important value for us in this tutorial is this circumference. The circumference of cog30 is three times the length of cog10. This means that if both cogs rotate 360° over the same time period, the teeth on cog30 will have covered three times the distance as the teeth on cog10, and therefore the teeth on cog30 are moving three times faster than cog10.
"cog30 is three times faster than cog10" is the same as "cog10 is 3 times slower than cog30".
In Fig.17, cog10 and cog30 are both rotated 90° over 25 frames - both are rotating at the same speed. However, the distance covered by the teeth on cog30 is clearly further than the teeth on cog10. Therefore the teeth on cog30 are moving three times faster than the teeth on cog10.
Customizing the Cogs
As the objective of this tutorial is rigging, the modeling aspect is kept to a minimum - the cogs are very simple. However, to make things more visually interesting in this tutorial, it's a good idea to customize the cogs as you create the gear system.
In Component mode [RMB], select the vertices of each cog and move [w] them to customize the thickness of each cog (Fig.18).
Remember to return to Object mode.
Create a polygon cylinder for the connecting spindle (Fig.19).
Don't forget to Delete History and Freeze Transformations after you have positioned and resized the spindle (cylinder). Then rename the spindle cylinder "gear01" (Fig.20).